The present invention relates to a camera back which is adapted to be mounted on a variety of cameras or optical devices and more specifically to a camera back adapted to hold self-developing type film and having means for discharging the film automatically upon taking a picture.
A camera back loaded with self-developing type films is well known in the art and is adapted to be mounted on large cameras such as press cameras and view cameras, microscope photographing devices or oscilloscope photographing devices. Self-developing type films are divided into two groups. In the first group, after exposure the film is caused to pass through the processing solution spreading means by pulling its leader and after a predetermined period of time the light shielding cover or the like is removed to obtain a visible picture. In the second group, after exposure the film is automatically discharged out of the photographing device through the processing solution spreading means. That is, in the second group, the developing treatment is automatically carried out and a part such as a light shielding cover to be removed after exposure is not employed. For such a camera back to be applicable to as many cameras or optical devices (hereinafter referred to as "photographing devices", when applicable) as possible, the distance between the mounting surface of the camera back by which the camera back is mounted on the photographing device and the film surface is short, and that, in order for the film surface of the camera back to be exactly positioned as the film surface of the photographing device, the camera back is mounted on the photographing device through an adaptor provided therefor. Furthermore, in order to improve the applicability of the camera back to a variety of photographing devices, it is essential that the mounting surface of the camera back has no protrusion, because the protrusion limits the photographing devices to which the camera back is applicable.
In the case of the camera back using the above-described films with leaders, the film is passed through the processing solution spreading means by pulling the leader. Accordingly, in this case, the positional relationship between the film surface and the processing solution spreading means is not strict, and the applicability of the camera back to a variety of photographing devices can be readily obtained. On the other hand, in the case of the camera back using the films which have no leaders, the exposed film is pushed into a processing solution spreading means, such as a pair of rollers driven by a motor, through a discharging slit formed in the film container by a pawl-shaped member which is adapted to enter into a narrow groove having a predetermined length cut in the front surface of the film container to thereby push the film towards the discharging slit, so that the film is discharged out of the camera back while being processed by the processing solution. Accordingly, in this case, the distance between the discharging slit of the film container and the processing solution spreading rollers must be shorter than the distance of movement (the length of the narrow groove in maximum) of the pawl-shaped member. In addition, the surface of a film which is at the photographing position, the discharging slit of the film container and the processing solution spreading means which might be the nipping region of the pair of processing solution spreading rollers must be substantially in one plane. Accordingly, it is considerably difficult to make the camera back applicable to a variety of photographing devices or the like.